The present invention relates to a process for preparing food products containing a high level of oleanolic acid, a compound which is derived from leaves of the olive tree. The present invention also relates to the obtained fortified products such as vegetable oils, in particular olive oil, spreads, mayonnaise, salad dressings and sauces.
Oleanolic acid (3-beta-hydroxy-28-carboxy-oleanen) belongs to the chemical compound class of the triterpenes. See FIG. 1 for its chemical structure. Olive leaves are a known source of oleanolic acid, containing up to 6.5 wt. %. Oleanolic acid has a low solubility in olive oil and may cause turbidity.
Oleanolic acid has a low solubility in olive oil and may cause turbidity.
Japanese Patent JP 9078061 (Derwent Abstract) discloses the use of a hydrolysed extract of olives and olive leaves as an antioxidant to be used for food, feed, cosmetics and drugs.
J. of the Am. Oil Chemists Soc. Vol. 73, no.3, pp. 371-374 (1996) gives a description of harvesting olive oil by pressing olive fruits at ambient temperature. For improving the olive oil flavour some olive leaves are added to the process mixture.
It is known that olive oil contains low amounts of oleanolic acid, although its presence is avoided because its low solubility in oil causes turbidity, particularly when the oil is stored below ambient temperature. Another useful component of olive oil is oleuropein, one of the native phenolic compounds which because of its bitter taste is removed from olive oil after pressing by washing or hydrolysis. Presently it is appreciated for its health supporting properties. Oleuropein is believed to have anti-inflammatory and anti-oxidant properties.
In olive oil which is obtained by conventional olive oil processing no levels higher than 300 ppm for oleanolic acid have been reported. Generally, olive oil is prepared by harvesting olive fruits and subjecting these to a malaxation treatment which comprises crushing and kneading the olives so that a mash is obtained containing the whole content of the olive fruit: solid matter, oil and an aqueous phase. Accidentally, some leaves of the olive tree may be encountered in the malaxation mixture. After malaxation the mash is separated into a liquid phase and a solid residue. The olive oil is separated from the aqueous phase in a decanting vessel or by centrifugation. The olive oil may be washed with water.
We have discovered the fortification of food products with oleanolic acid. The nutritional potential of this compound is based on its many valuable health supporting properties (see EP 94 517). The invention provides an economical and simple process for the fortification of food products with oleanolic acid, in particular of a vegetable oil such as olive oil. According to the present invention an olive oil or olive residue oil is prepared according to a conventional process, but with the exception that
the malaxation mash contains 5-50 wt. % of olive leaves
the malaxation treatment is carried out at an elevated temperature being 24-60xc2x0 C.
This adapted process results in an olive oil or an olive residue oil which contains at least 300 ppm of oleanolic acid.